If you see black spots growing in your pool, it is a sign of the beginning of black algae and you will want to treat it immediately. The longer you let it go, the harder it will be to eliminate it. Black algae generally penetrate porous pool surfaces like concrete and gunite. Once these surfaces are infested with black algae, it will take time and persistence to eliminate it. Black algae are generally not an issue with smooth-surfaced pools like fiberglass and vinyl. This guide provides a step-by-step procedure for eliminating black algae.
Doyle Posted: 8/10/2021
I have a 10K gal pool. We have a shallow area that is about 6 inches deep and I am getting some black algae dots in that area. I am using a PoolRX and when I had the water tested last week it showed 0.9 ppm copper. I shock weekly and try to keep Free chlorine between 1 and 2 ppm. Cyanuric is 42 ppm and I use liquid chlorine. My phosphates ran very high on this last test at 2500 ppb. I am using a steel brush in the shallow area where the dots appear but unsure what to do next. Water temp is at 85-87F.Reply
InyoPools Product Specialist Matt S. Posted: 8/11/2021
At a glance, I'd say your phosphates are not the cause of the algae, but they are definitely a catalyst to its growth. I'd try a phosphate remover like PhosFree Extra Strength along with your doses pool shock and a black algae-specific algaecide. A metal sequestrant would be helpful on the backend to control that copper level.Reply
Dale Posted: 4/29/2019
I have drained my pool had black last fall, never could get rid of it all. Now I can see the black on several areas on the bottom I am patching a couple of holes I am going to acid wash first, wiil the acid wash be enough and I am going to paint it ?Reply
InyoPools Product Specialist Matt S. Posted: 4/30/2019
Hello Dale - yes, the acid wash should clear up any lingering algae.Reply
Bill Posted: 3/21/2019
We have had black algae since we moved into our house in November. I have tried everything the local pool store recommended. But I am loosing the battle. The only thing we feel left to do is replanted. Any other suggestionsReply
InyoPools Product Specialist Robert M. Posted: 3/25/2019
Bill - Have you tried silver algaecide? I used this a few years back when the normal black algaecides were not working and it did a great job.Reply
Anonymous Posted: 8/4/2021
Where do you find silver algaecide? I only see blackReply
InyoPools Product Specialist Matt S. Posted: 8/5/2021
We usually carry silver algaecide but our supplier is out of stock at the moment. But a quick online search should bring up quite a few possibilities.Reply
Anonymous Posted: 3/25/2019
No I have used algeatrane but not silver algaecideReply
Katie Posted: 1/7/2019
Do you do the step by step all in one day? Like add all the chemicals in the same day at the same time or do I do one one day, and wait and do the rest the next? Just wasn't for sure if I was suppose to mix all the chemicals together at the same time?Reply
InyoPools Product Specialist Robert M. Posted: 1/10/2019
Hello Katie - You wouldn't want to mix all the chemicals at once. If you're using a black algaecide, follow the directions on the bottle. In most cases, the pH is adjusted first, followed by chlorine, and then the algaecide. You can separate each one by a couple hours.Reply
InyoPools Posted: 9/25/2018
Hello MN - It sounds like you are doing everything correct. We would recommend using a silver algaecide to remove black algae. The silver algaecide seems to work well when the black algaecide does not.Reply
MN Posted: 9/21/2018
I have been fighting w/ Black Algae for several weeks now on the floor of my pebble tech pool - I wire brush 2-3 times a day (so much so that I have loosened alot of pebbles :-( ), I scrub chlorine tabs directly on spots, have my FC up at 7+, and have done 2 diff treatments using 2 diff brands of 32oz Black Algaecides and, of course, cleaned filters prob every 3-4 days... It is not all over the floor of my pool but very prominent where it is - dark black clusters. Any ideas what I am doing wrong and why it won't go away...Reply
InyoPools Posted: 8/16/2018
Hello Shonda - Black algae usually occurs in small pits when the chlorine level is low. As far as getting rid of those spots, I recommend using a silver algaecide. This algaecide can be used with water in the pool.Reply
InyoPools Posted: 8/16/2018
As far as I know, the only way to treat black algae underneath an inground pool liner is to remove the existing liner and treat the algae. After the algae is treated you can roll on an algae preventative before installing a new liner.Reply
Anonymous Posted: 8/6/2018
Help! The black algae is Under the liner of my 20X40 in ground pool. It shows up as big black areas in the pool. Scrubbing doesn't work. It keeps getting worse. I've tried shocking, algaecide but nothing works. It just stays there. This spring when I opened the pool, there was nothing on it, but now it's a mess. Is there anything I can do besides replacing the liner and treating the ground underneath (which I did a few years ago) Now the same problem is back.Reply
Shonda Posted: 7/30/2018
We have just discovered we have black algae spots on the bottom of our light-colored gunnite saltwater pool--even though we have it serviced every week and it's only 3 years old. I'm now panicked as I want to get rid of this as quickly as possible before it gets worse. Are we better off draining the pool and scrubbing it and killing it? Also--what causes black algae? We've never had it before and are wondering if we did something wrong?Reply
Melanie Posted: 5/15/2018
I have a fiberglass pool about 18yrs old. Yes, I have black algae. I live in the desert and did drain because our water table is so low I was told it's OK. I have been on my hands and knees scrubbing w/ chlorine tab and will follow your advice and refill and shock and treat w/ black algae killer (did not work first time from major chain. They told me pretty much hopeless and to replace pool!) and keep brushing. Hope your instructions are the same for fiberglass, although I know we are now supposed to get it. My luck. Thanks for the thorough instructions. I am encouraged.Reply
Inyopools Posted: 1/7/2018
john - I wouldn't recommend swimming in any water that contains algae. You run the risk of getting it into your eyes or ingesting it into your lungs.Reply
john Posted: 1/4/2018
What stages can we still swim in the pool?Reply
InyoPools Product Specialist Dennis R. Posted: 8/28/2017
Gina - The process is the same for salt water pools.Reply
Santiago Posted: 10/1/2021
Could you please recommend what chemicals to use to treat black algae spots in a pool with a salt chlorinator? I understand there are some chemicals that are not compatible with a salt pool.Reply
InyoPools Product Specialist Matt S. Posted: 10/1/2021
All of the chemicals and cleaners we mention in this guide can be used with traditional chlorine or saltwater pools.Reply
Gina Posted: 8/28/2017
What about a Salt Water Pool? Is the process different?Reply
InyoPools Product Specialist Dennis R. Posted: 7/21/2017
GUSGUS - We use to sell pools that held a chlorine tablet at the end to scrub algae on the bottom floor, but they were ineffective. You might see if you can find something like that on the internet. Other than that, I would agree with you. The most effective way to eliminate black algae on the bottom of a small pool would be to drain it, scrub it for two or three days, refill the pool and shock to 2-3 more days with frequent brushing and daily cleaning of the filter.Reply
GUSGUS Posted: 7/19/2017
If I have black algae on the bottom of my pool some places hard to reach, would draining it and cleaning it be easier to remove the algae?Reply
InyoPools Product Specialist Dennis R. Posted: 7/7/2017
Irene - You have to keep at removing the black algae. Initially, brush every black spot 3-4 times the first day then 2-3 times a day for the rest of the treatment period. Remember to clean your filter every day too.Reply
Irene Posted: 7/6/2017
I brushed some of the algae last night, today we'll finish and start chemicals, etc. do I have to re-brush the ones I did last night? i.e. how long before algae coated roots start again? I know I brush 3 times per day during treatment..Reply
InyoPools Product Specialist Dennis R. Posted: 7/5/2017
The goat - Yes, you can use a steel brush on a pebble tec surface. The key to eliminating black algae is persistence. Black algae tends to embed itself into the wall of the pool. You have to brush it to remove the hard heads of the algae to allow the chemicals to get below the surface. Brush the algae spots, then use half of chlorine tablet to rub chlorine directly into the algae spots before adding chemical. Then repeat this process every day for 3-4 days.Reply
The goat Posted: 7/3/2017
I have a dark finish pebble tec pool which also runs on a DE filter. I got black algae as soon as we moved into this house and the filter broke. Can I use a stainless steel brush on a pebble tec surface? Any other recommendations as to getting rid of this stuff?Reply
Anonymous Posted: 6/23/2017
Clear and straight to the point instructions. Worked great, thank you!Reply
Anonymous Posted: 5/25/2017
Inyo pools got it right.I should have done a before and after with photos. I did everything they said and my black algae is contained.
Reply
InyoPools Product Specialist Dennis R. Posted: 4/8/2017
Anonymous (algae) - I'm not sure what you mean by "My algae is 12 down" but here is a good link to a recent video on "How to Clean a Green Pool".Reply
Anonymous Posted: 4/5/2017
My algae is 12 down what did do for that?Reply
joe Posted: 3/19/2017
very helpful, contains a lot of useful, practical information.THANK YOUReply
Anonymous Posted: 11/9/2016
thank you...good tip..keep the good work..Reply